1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copying machine, facsimile device, and a printer. Particularly, the present invention relates to a cleaning device that has a cleaning blade or other cleaning member for coming into contact with a surface of an image carrying body serving as a surface moving member of the image forming apparatus to remove unnecessary objects adhering to the surface moving member, as well as to a process cartridge having this cleaning device.
2. Description of the Related Art
These types of conventional image forming apparatuses normally have a surface moving member, which is, in other words, an image carrying body such as a photosensitive drum and an intermediate transfer belt, and a surface transfer member such as a recording material conveying belt. Generally, because various problems are caused when an unnecessary object adheres to a surface of such a surface moving member, cleaning means for removing the adhered object from the surface of the surface moving member is required. As this cleaning means, a blade type cleaning device has been widely used. This blade type cleaning device with a simple configuration and excellent adhered object removing performance pushes a cleaning blade made of polyurethane rubber or other elastic member against the surface of the surface moving member to remove the adhered object from the surface.
The cleaning devices disclosed in the following patent publications are known as such a cleaning blade type cleaning device.
Japanese Patent Application Publication No. 2007-108481 (to be referred to as “Prior Art 1” hereinafter)
Japanese Patent Application Publication No. S60-198574 (to be referred to as “Prior Art 2” hereinafter)
Japanese Patent Application Publication No. 2006-178164 (to be referred to as “Prior Art 3” hereinafter)
Japanese Patent Application Publication No. 2008-233319 (to be referred to as “Prior Art 4” hereinafter)
Japanese Patent Application Publication No. 2008-096965 (to be referred to as “Prior Art 5” hereinafter)
Incidentally, as the blade type cleaning device, for example, two types of the cleaning devices are known: the trailing type cleaning device disclosed in Prior Art 2 described above, and a counter type cleaning device disclosed in Prior Art 3 described above. Generally, in the counter type cleaning device, the abutment pressure of the cleaning blade on the surface of the surface moving member can be made higher than that of the trailing type cleaning device. Therefore, the advantage of the counter type cleaning device is that the performance for removing the adhered object on the surface of the surface moving member is higher than that of the trailing type cleaning device. For this reason, the counter type cleaning device is adopted when high removing performance for removing the adhered object is required. Particularly, in a recent electrophotographic image forming apparatus, toner that has a spherical shape and small diameter, such as, particularly, polymer toner, is usually used, and high removing performance is required in order to remove this type of toner as the adhered object. Thus, because the removing performance of the trailing type cleaning device is not sufficient, the counter type cleaning device is adopted.
In such a counter type cleaning device, when the amount of abutment of the cleaning blade against the surface of the surface moving member from a supporting member supporting the cleaning blade is increased in order to raise the abutment pressure of the cleaning blade on the surface of the surface moving member, as disclosed in Prior Arts 1 and 2 described above, the cleaning blade is bent and consequently the contact area between the cleaning blade and the surface of the surface moving member increases. Therefore, the problem is that the abutment pressure of the cleaning blade against the surface of the surface moving member ends up decreasing.
Therefore, in order to increase the abutment pressure, Prior Arts 3 and 4 described above, for example, proposes a configuration in which the amount of abutment of the cleaning blade from the supporting member supporting the cleaning blade is made zero. In this configuration, because the cleaning blade deforms only by its own elasticity, the contact area between the cleaning blade and the surface moving member is prevented from increasing, and the cleaning blade is brought into abutment against the surface moving member by high pressure, improving the cleanability of the abutting part. However, because the cleaning blade deforms only by its own elasticity, simply using the configuration of reducing the amount of abutment to zero makes it difficult for the cleaning blade to follow a change in the position of the surface moving member that is caused when the surface transfer member is moved. When the part accuracy or assembly accuracy of the cleaning blade or the surface moving member is degraded, the cleaning blade cannot abut evenly against the surface of the surface moving member in the longitudinal direction of the cleaning blade, and therefore it is difficult to secure even cleanability.
Prior Art 4 proposes a technology for improving the followability of the cleaning blade by providing a degree of freedom to the support of the supporting member supporting the cleaning blade. For example, in order to clean small-diameter toner or spherical toner in an excellent manner, it is desired that the cleaning blade be brought into abutment more evenly against the surface of the surface moving member, so that the reliability of the cleaning performance and the reliability of the image formation performance can be improved.
In the conventional counter type cleaning device, on the other hand, when the cleaning blade is pressed strongly against the surface of the surface moving member to achieve high removing performance for removing the adhered object, the surface moving member or the cleaning blade itself becomes worn, reducing the life of the surface moving member or the cleaning blade.
In order to solve such problems, the cleaning device disclosed in Prior Art 5 is known. In this cleaning device, a warpage restricting member restricts warpage of a cleaning blade that is generated when this cleaning blade that is long in a width direction of a surface moving member is pressed against the surface of the surface moving member. As a result, compared to a cleaning blade whose warpage is not restricted, the length of an abutting part in a surface moving member surface moving direction between the cleaning blade and the surface of the surface moving member (to be referred to as “abutment width” hereinafter) can be reduced. In other words, in the conventional counter type cleaning device in which the warpage of the cleaning blade is not restricted, warpage and deformation of the cleaning blade occur by pressing the abutting side of the cleaning blade against the surface of the surface moving member. The greater the warpage or deformation of the cleaning blade gets, the longer the abutment width becomes. In this cleaning device, because the warpage of the cleaning blade is restricted by the warpage restricting member, the abutment width is mainly determined by the deformation of the cleaning blade only. Therefore, unlike the conventional counter type cleaning device in which the warpage of the cleaning device is not restricted, this cleaning device can reduce the abutment width. Further, even when the same amount of abutment pressure is used, the shorter the abutment width is, the less the surface moving member or the cleaning blade wears. Hence, unlike the counter type cleaning device in which the warpage of the cleaning blade is not restricted, this cleaning device can prevent the surface moving member or the cleaning blade from becoming worn.
However, in an image forming apparatus, the positional relationship between the surface moving member and the cleaning blade changes due to deformation of members that is caused by the manufacturing tolerances or environmental variations within the image forming apparatus main body. In the cleaning device disclosed in Prior Art 5, the change in the positional relationship between the surface moving member and the cleaning blade may not be able to appropriately maintain the state of abutment between the surface moving member and the cleaning blade in the longitudinal direction of the cleaning blade. In short, in some sections this abutment in the longitudinal direction may not be formed. In the configuration in which the warpage of the cleaning blade is not restricted, the warpage of the cleaning blade is eliminated in spite of the change in the positional relationship, and consequently the change in the positional relationship is absorbed and the state of abutment can be maintained. However, in the configuration of this cleaning device in which the warpage of the cleaning blade is restricted, the cleaning blade does not warp, and therefore it is difficult to correct the change in the positional relationship. When adopting the configuration in which the warpage of the cleaning blade is restricted, such as the configuration of this cleaning device functioning as the cleaning means for cleaning the surface moving member, the cleaning device needs to have a configuration for absorbing or correcting the change of the positional relationship, otherwise the state of abutment in the abutting part cannot be maintained over time, due to the change in the positional relationship. Consequently, a problem arises that some sections on the surface moving member cannot be cleaned sufficiently.
Therefore, in order to solve the problems described above, in the cleaning device disclosed in Prior Art 4, engaged means provided in a holding member for folding the cleaning blade is engaged with engaging means supported in the device main body, with a degree of freedom, whereby the holding member can be displaced with respect to the device main body. Because the holding member is displaced with respect to the device main body, a change in the positional relationship between the members that is caused by the manufacturing tolerances or environmental variations can be corrected, and the state of abutment between the surface moving member and the cleaning blade can be maintained. As a result, the occurrence of abutment variations in the longitudinal direction of the cleaning blade can be prevented, and the state of abutment between the cleaning blade and the surface of the surface moving member can be maintained over time.
However, even with the configuration of this cleaning device in which the engaged means of the holding member and the engaging means on the device main body side are engaged with each other with a degree of freedom, in some cases the state of abutment in the abutting part cannot be maintained due to the change in the positional relationship. The reason is as described hereinafter.
First, a section that can be displaced integrally in relation to the device main body configured by the cleaning blade and the holding member is formed as a blade unit. As with the cleaning device described in the previous application, the engagement between the engaged means of the holding means and the engaging means on the device main body side is achieved in two sections of both ends of the holding member in a longitudinal direction thereof. Further, the positions of the cleaning device main body and surface moving member are fixed. In this case, when four positions are defined in the device main body, that is, when the positions on the both ends in the longitudinal direction of an abutting side where the cleaning blade abuts against the surface moving member and the positions of the engaging means in the two sections in the holding member are defined, the positional relationship between the blade unit and the device main body can be specified.
In consideration of the case where two objects with which the deformation can be neglected are brought into contact with each other and positioned, they can be positioned by bringing three points into contact with one another outside a straight line. Furthermore, when a straight line that connects two points out of the three contacting points is taken as a positioning reference line, and one of the two objects rotate around the abovementioned reference line with respect to the other object, the remaining one point out of the three points becomes a point that is brought into contact with the two objects.
Then, the relationship between these two objects is considered as the relationship between the blade unit and the cleaning device. When the two objects are brought into contact with the device main body in three sections out of the four points (including the surface moving member fixed to the device main body), the position of the remaining one section in relation to the device main body is determined depending on the positions of the three sections. Therefore, when the straight line connecting the engaged means on the two sections of the holding member becomes the abovementioned reference line, in a state in which one end of the abutting side in the longitudinal direction abuts against the surface moving member, the position of the blared unit in relation to the device main body is determined based on three points, that is, the two engaged means and one abutting end of the abutting side. When there is a change in the positional relationship between the abovementioned members in the configuration where the position of the blade unit is determined by the three points, out of the both ends of the abutting side of the cleaning blade, the one end configuring the positioned three points and the other end that does not configure the three points are abutted in a different state. In some cases the other end does not come into contact with the surface moving member.